Study of the activation process of Mg-based hydrogen storage materials modified by graphite and other carbonaceous compounds
A nanocomposite (Mg–V)nano made of 90 wt% Mg and 10 wt% V was prepared by high-energy ball-milling during 40 h. The activation characteristics of (Mg–V)nano are rather poor, the hydrogen content [H] reaching 4 wt% after more than 100 h (t4wt%) following the initial exposure of the material to H2. Ad...
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Published in | Journal of materials research Vol. 16; no. 10; pp. 2893 - 2905 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
New York, USA
Cambridge University Press
01.10.2001
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Online Access | Get full text |
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Summary: | A nanocomposite (Mg–V)nano made of 90 wt% Mg and 10 wt% V was prepared by high-energy ball-milling during 40 h. The activation characteristics of (Mg–V)nano are rather poor, the hydrogen content [H] reaching 4 wt% after more than 100 h (t4wt%) following the initial exposure of the material to H2. Adding 9 wt% graphite to (Mg–V)nano and resuming the milling operation for 30 min leads to the formation of (Mg–V)nano /G, which exhibits a t4wt% value of only 10 min. The addition of more than 9 wt% graphite to (Mg–V)nano does not lead to any significant reduction of the t4wt% value. However, extending the milling period with graphite over 30 min leads to a steady increase in t4wt% and, thus, to a deterioration of the activation characteristics. Comparison of the behavior of graphite with other C-based compounds revealed that perylene (C20H12) and pentacene (C22H14), which are made of linked benzene rings, and thus have a 2D structure similar to that of the graphene sheet, are as effective as graphite in improving the activation characteristics of (Mg–V)nano. A structural investigation of (Mg–V)nano /G as a function of the milling time through both C 1s core-level x-ray photoelectron spectroscopy and C K edge x-ray absorption near-edge spectroscopy has shown that the integrity of graphite is progressively lost as the milling period is extended over 30 min. On the basis of these results, it is hypothesized that the adsorption of graphene layer on freshly created Mg surfaces and the formation of highly reactive C species during milling prevents the re-formation of the surface oxide layer responsible for the poor activation characteristics of untreated (Mg–V)nano |
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Bibliography: | istex:B28BB39D265A798FA09E4DC86336A39C6AEAC762 ark:/67375/6GQ-XJ8V01TW-H ArticleID:06625 PII:S0884291400066255 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0884-2914 2044-5326 |
DOI: | 10.1557/JMR.2001.0398 |